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  • 1
    Electronic Resource
    Electronic Resource
    Analysis of the sign reversal of the second-order molecular polarizability in polymethineimine chains (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 115 (2001), S. 6766-6774 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The second-order polarizability tensor (β) components of polymethineimine oligomers have been computed with the semiempirical intermediate neglect of differential overlap (INDO) coupled either to sum-over-states (SOS) or finite-field real space approach. Our goal is to rationalize the sign reversal of the longitudinal β component with chain length. The INDO results are shown to compare well with the values obtained from previous ab initio calculations. Using a four-state SOS model that reproduces correctly the evolution of β with chain length, we demonstrate that the shape of the β curve can be explained as resulting from the competition between two contributions of opposite signs. In the framework of a real-space approach, those contributions are found to correspond to bond charge and bond polarization phenomena. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1401822
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  • 2
    Electronic Resource
    Electronic Resource
    Comment on "Calculation of ab initio dynamic hyperpolarizabilities of polymers" [J. Chem. Phys. 110, 2717 (1999)] (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 1616-1617 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We evaluate the static and dynamic electronic longitudinal polarizability and first hyperpolarizability of infinite poly-water by using the same geometry, the same orientation and the same basis set as Otto et al. but by applying the finite oligomer technique. We show that for the first hyperpolarizability, the polymeric values per unit cell calculated by Otto et al. are inconsistent by several orders of magnitude with respect to the infinite oligomer limit. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.480727
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  • 3
    Electronic Resource
    Electronic Resource
    Long-range effects in optimizing the geometry of stereoregular polymers. II. Hydrogen fluoride chains as a working example (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 5324-5330 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We use linear hydrogen fluoride chains to evaluate the efficiency of the long-range approach developed in the first paper of this series. A wide panel of tests and comparisons are carried out in order to understand the influence of the parameters on the quality of the forces and the accuracy of the optimized geometry. The long-range corrections are demonstrated to be essential for tight optimizations as well as to fasten the calculation procedure. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.479791
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  • 4
    Electronic Resource
    Electronic Resource
    Long-range effects in optimizing the geometry of stereoregular polymers. I. Formalism (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 5306-5323 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We develop an original methodology to calculate analytically the long-range (LR) Coulombic effects to be included in Hartree–Fock forces computed on stereoregular polymers. The technique presented, based on multiple Taylor series expansions, is completely general and can be easily extended to all orders of expansion and to geometrical derivatives of higher order. In the McMurchie Davidson or similar schemes, the LR terms are added directly to Hermite integrals and LR effects are naturally considered during the computation of the energy and its derivatives. Each type of derivative (nuclear-repulsion energy, overlap and kinetic energy integrals, electron–nuclear attraction and two-electron integrals) is examined to quantify the impact of LR corrections. It turns out that the lattice sums of the gradients evaluated on a model macromolecule converge much faster when including those corrections. In addition, the dependence of the energy with respect to the unit cell length is for the first time considered in full details. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.479790
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  • 5
    Electronic Resource
    Electronic Resource
    Ab initio static polarizability and first hyperpolarizability of model polymethineimine chains. II. Effects of conformation and of substitution by donor/acceptor end groups (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 5076-5087 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: An ab initio coupled Hartree–Fock study has been carried out on polymethineimine (PMI) oligomers with an increasing number of unit cells (up to N=20) to determine the effect of conformational differences, and of end-capping by a strong donor-acceptor pair, on the static electronic longitudinal polarizability (αL) and first hyperpolarizability (βL). For the unsubstituted polymer the differences in βL per unit cell among the four conformations examined—trans-transoïd (TT), cis-transoïd (CT), trans-cisoïd (TC) and helical (HEL)—are large. βL/N is positive for the CT polymer, in contrast with the other conformers and with μL/N, which is negative in all cases. The TC polymer has the largest |βL|/N despite having a relatively small αL/N. Substitution of a strong acceptor (NO2) at the carbon end of an oligomer and a strong donor (NH2) at the nitrogen end results in a large increase of βL/N for small/medium N. In the case of the TT and, particularly, the CT conformer this leads to a maximum in |βL|/N vs N at N=4–6, which is substantially greater in magnitude than the one at N=∞. The latter is unaffected by substitution. We compare the [βL(N)/N]max obtained at intermediate N for substituted PMI chains with those calculated for linear polyenes and other π-conjugated oligomers. The shape of all the βL/N vs N curves obtained is fit to a function which yields parameters characterizing the delocalization along the backbone, the unit cell asymmetry, and the asymmetry of the chain ends.© 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.474892
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  • 6
    Electronic Resource
    Electronic Resource
    Ab initio band structure of polymethineimine isomers (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 1023-1030 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Ab initio crystal orbital calculations have been performed on stereoregular polymethineimine (PMI) at the restricted Hartree-Fock/6-31G level. Since the optimized geometries of the parent oligomers show only small energy differences, four isomers, namely, trans-transoïd (TT), cis-transoïd (CT), trans-cisoïd (TC) and helical (HEL) have been studied to point out the geometry-dependences of the band structure, density of states (DOS) and polarizability. Some of these could be helpful for identifying the isomers. It turns out that the DOS makes the TT and CT isomers distinguishable, whereas the TC and HEL isomers present very similar DOS. Moreover, it is shown that the longitudinal polarizability per unit cell increases in the order HEL, TC, CT and TT. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.475497
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  • 7
    Electronic Resource
    Electronic Resource
    Electron nuclear dynamics of proton collisions with methane at 30 eV (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 6146-6155 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The reactive collisions of protons with methane molecules at 30 eV in the laboratory frame are studied with the electron nuclear dynamics (END). The results from this theoretical approach, which does not invoke the Born–Oppenheimer approximation and does not impose any constraints on the nuclear dynamics, are compared to the results from time-of-flight measurements. Total differential cross sections and integral cross sections as well as fragmentation ratios and energy loss spectra are discussed.© 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.474343
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  • 8
    Electronic Resource
    Electronic Resource
    Yeast adenylate cyclase catalytic domain is carboxy terminal (1986)
    Springer
    Current genetics 10 (1986), S. 343-352 
    Details
    ISSN: 1432-0983
    Keywords: Cyclic AMP ; General control of amino acids biosynthesis ; Yeast adenylate cyclase ; Yeast RAS sequences ; Regulatory nucleotide sequences
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Subcloning of DNA fragments from the gene coding for yeast adenylate cyclase has permitted, after complementation studies in S. cerevisiae cdc35 mutants as well as E. coli cya mutants, to identify the sequence coding for the catalytic domain of the protein. No homology is found between the yeast cyclase catalytic domain and the homologous domain found in E. coli adenylate cyclase. Analysis by Northern blotting of yeast polyA mRNA has shown the existence of multiple transcriptional products of the gene. A putative origin of a major transcript (3.5 kb) would allow synthesis of a ca. 100,000 dalton protein exhibiting cyclase activity in its carboxy terminal domain, and having 7 repeats of 17 amino acids at its amino terminal end. Several noteworthy features, including the possibility of transcriptional control by the general control of amino acids biosynthesis, are present at this putative origin. Data are presented suggesting that a much longer gene product might also be synthesized from the CDC35 gene. Neither the gene organization nor the amino acid sequence of the protein does display any homology with the adenylate cyclase gene and protein of Escherichia coli. This suggests a case of evolutionary convergence for the synthesis of CAMP in prokaryotes and eukaryotes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00418405
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  • 9
    Electronic Resource
    Electronic Resource
    The isolation and structure of 13,18-dehydroglaucarubinone, a new antineoplastic quassinoid fromSimarouba amara (1978)
    Springer
    Cellular and molecular life sciences 34 (1978), S. 1122-1123 
    Details
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary An investigation of the Guyana plantSimarouba amara Aubl. (Simaroubaceae) for antineoplastic quassinoids led to isolation and structural determination of the new quassinoids 2′-acetylglaucarubine (1a) and 13,18-dehydroglaucarubinone (2). The previously known 2′-acetylglaucarubinone (3a) and glaucarubinone (3b) were also obtained. The new quassinoid2 was found significantly to inhibit growth of the murine lymphocytic leukemia P388.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01922904
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  • 10
    Electronic Resource
    Electronic Resource
    Isolation and characterization of DNA sequences from Triticum aestivum which function as origins of replication in Saccharomyces cerevisiae (1983)
    Springer
    Plant cell reports 2 (1983), S. 175-178 
    Details
    ISSN: 1432-203X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Recombinant YIp5 plasmids with the DNA from Triticum aestivum are capable of autonomous replication in Saccharomyces cerevisiae. The URA transformants are unstable without selection pressure, and transformation of yeast cells with these plasmids occurs at high frequency. The cloned sequences were characterized and analyzed to state their belonging to Triticum tribe.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00270096
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